The invention relates to a method for operating a storage catalytic converter of an internal combustion engine, especially of a motor vehicle, wherein the storage catalytic converter is coupled to a three-way catalytic converter and wherein the storage catalytic converter is loaded with and unloaded of nitrogen oxides. Likewise, the invention relates to a control apparatus for an internal combustion engine, especially of a motor vehicle, as well as an internal combustion engine especially for a motor vehicle.
A method of this kind, a control apparatus of this kind and an internal combustion engine of this kind are, for example, known for a so-called gasoline direct injection. There, the fuel is injected into the combustion chamber of the engine in a homogeneous operation during the induction phase or in a stratified operation during the compression phase. The homogeneous operation is preferably provided for the full-load operation of the engine while the stratified operation is suitable for the idle and part-load operation. In such a direct injecting internal combustion engine, a switchover is made between the mentioned operating modes, for example, in dependence upon the requested torque.
It is especially important to have a storage catalytic converter especially for carrying out the stratified operation. With the storage catalytic converter, developing nitrogen oxides can be intermediately stored in order to reduce the same during a subsequent homogeneous operation. This storage catalytic converter is loaded with the nitrogen oxides during stratified operation and is again unloaded during homogeneous operation. This loading and unloading as well as thermal loads and contaminations lead to a deterioration of the storage catalytic converter. Diagnostic methods for the storage catalytic converter are carried out to monitor this deterioration.
It is an object of the invention to provide a method for operating a storage catalytic converter of an internal combustion engine with which the deterioration of the storage catalytic converter can be accurately monitored.
This object is achieved with a method of the above-mentioned type in accordance with the invention in that a diagnosis of the storage catalytic converter is carried out below a temperature at which the three-way catalytic converter does not yet operate. The object is solved correspondingly with a control apparatus and an internal combustion engine of the type mentioned initially herein.
If the diagnosis is carried out at a temperature, for example, below approximately 250 degrees, then this affords the advantage that the three-way catalytic converter has no influence yet on the diagnosis of the storage catalytic converter because the operating region of the three-way catalytic converter has not yet been reached. The diagnostic result for the storage catalytic converter is therefore not made incorrect but is, with high accuracy, referred exclusively to the storage catalytic converter.
In an advantageous embodiment of the invention, the diagnosis is carried out above a temperature at which the storage catalytic converter operates. In this way, it is ensured that the storage catalytic converter is in its own operating region and the diagnosis of the storage catalytic converter can be carried out reliably and accurately.
It is especially advantageous when the temperature of the storage catalytic converter is measured by a temperature sensor. In this way, the above-mentioned temperature region is especially easily determined and monitored.
Of special significance is the realization of the method of the invention in the form of a control element which is provided for a control apparatus of an internal combustion engine, especially of a motor vehicle. A program is stored on the control element which can be run on a computing apparatus, especially on a microprocessor, and is suitable for executing the method in accordance with the invention. In this case, the invention is therefore realized by a program stored on the control element so that this control element, which is provided with the program, defines the invention in the same way as the method for whose execution the program is suitable. As a control element, an electric storage medium is especially applicable, for example, a read-only-memory or a flash memory.
Further features, possibilities of application and advantages of the invention will become apparent from the description of the embodiments of the invention which follow and which are shown in the figures of the drawing. All described or illustrated features form the subject matter of the invention individually or in any combination independently of the composition thereof in the patent claims or their dependency as well as independently of their formulation in the description or their illustration in the drawing.